1. Technical Field
The present invention relates to actuators and, more particularly, to a pulley actuator.
2. Description of Related Art
A conventional pulley actuator to be used in long-travel applications, such as a lifting mechanism for hospital beds or tables, is shown in FIG. 1. The pulley actuator is driven by a motor 11 and implements a reducing mechanism 12 to transmit the rotational driving force to a screw 13 so that the rotating screw 13 is enabled to stretch or retract a guide rod 14 coupled therewith. A first tube 15, a second tube 16, and a third tube 17 are telescoped in an inward order and jointly shield the screw 13. A first pulley 141 is provided at a distal end of the guide rod 14. A first rope 142 has one end fixed to the reducing mechanism 12 while having an opposite end mounted around the first pulley 141 to be then fixedly coupled with the distal end of the guide rod 14 and adjacent to the first pulley 141. A second pulley 143 is settled aside a proximal end of the guide rod 14. A second rope 144 has one end fixed inside a distal end of the third tube 17 while having an opposite end mounted around the second pulley 143 to be then fixedly inside a distal end of the first tube 15.
The actuator depicted in FIG. 1, however, has its defects.
Since the pulley actuator employs two pulleys and two ropes for transmission, the ropes need separate installation and adjustment in each time of fabrication or maintenance, thus inconveniencing its user.
Besides, to disassemble the installed pulley actuator that has the first tube 15 coupled with the reducing mechanism 12 and the third tube 17 fixed to or welded to a bed or a table, the motor 11, the reducing mechanism 12, the first tube 15, the second tube 16 and the third tube 17 have to be detached successively, which is also detrimental to convenient maintenance.